Certain types of circuits exhibit less than ideal responses. For example, a phase modulator can accept a digital phase and/or amplitude input to control the phase/amplitude of a radio frequency signal. Non-linearity in the phase modulator can result in the output being different than intended. While some techniques for compensating for such non-idealities are known, challenges are presented when systems are to be integrated onto a chip. Challenges can include: substrate area limitations, radiation hardening requirements, inaccessibility of components for adjustment/tuning, etc.
Substrate area limitations become an issue when attempting to implement a prior art lookup table on an integrated circuit. Often the lookup table includes several logic gates, each of which consumes space on the chip. Often a chip designer has to balance area limitations with less than desired bit resolution of various compensation techniques.